MAPT and Alzheimer disease: In a study on LGI1 encephalitis, almost one-third of patients had CSF levels of Aβ42 below the cut-off for AD; however, median CSF Aβ42 was higher compared to AD and similar to CJD and psychiatric patients, and no patient with LGI1 encephalitis had a true CSF AD profile (i.e., reduced Aβ42 along with increased T-tau and P-tau181) [140].